Infectious Bovine Keratoconjunctivitis (IBK; ‘pinkeye’) is the most common eye disease of beef cattle in California. Few studies have examined mucosal vaccination with M. bovis antigens and the ability of such vaccines to prevent IBK. The overarching hypothesis of the proposed study is that calves vaccinated intranasally with carboxy MbxA (referred to as just ‘Mbx A’ below) will have a significantly reduced cumulative proportion of corneal ulcerations associated with naturally occurring IBK versus control calves.